Thoughts on "Marathon" Workouts?

So, recently a 3-days-a-week program has been working really well with my schedule, but because I have a pretty high work capacity and want to get a lot of work done with this lower frequency programming, I end up spending almost 2 hours in the gym some days. Some of my friends have been telling me this is overdoing it, while I've basically just responded "Eh, I feel pretty good". My workouts always start with multiple heavy compound movements and then I do a bunch of accessory work, typically hitting the whole body over the course of a workout. Anyone have any good insight on if this is a counterproductive style of training?